1. Field of Invention
The subject of the present invention is a device for supplying hydraulic power to a rotary percussive drilling apparatus.
2. Description of Related Art
The apparatus to which it relates is used for drilling holes intended for extracting rocks and ores, and comprises a drilling tool given a rotational movement and driven in percussion using an impact device which acts independently of the rotation. The apparatus is mounted on an advance device which allows the tool to create a bearing force on the ground during drilling.
FIG. 1 of the attached schematic drawing depicts a device of known type.
This device comprises a perforating hammer 2 equipped with a tool 3 associated with a device for driving in rotation 4 and with an impact device 5. A distributor 6 allows the reciprocating movement of the piston 7 of the impact device 5 to be performed. The perforated hammer is mounted so that it can move with respect to the land which is to be drilled, with the aid of an advance system mounted on slides. The advance system 9 comprises a hydraulic ram, the rod 10 of which bears against a fixed point 12. The advance system is guided by slides 13.
The apparatus also comprises a device 14 for sucking up debris driven by a hydraulic motor 15.
Various movements are obtained from a source of hydraulic liquid under pressure through a flow splitter 16, for example of the gear or static type, which, via four distributors 17, 18, 19 and 20 respectively, supplies the hydraulic motor of the device for driving in rotation, the impact device, the ram of the advance  system, and the hydraulic motor of the device for sucking up debris.
Connections are made via a series of hoses.
Known rotary percussive drilling apparatuses are characterized by hydraulic flow rates and pressures which differ according to the movements instigated. The highest pressure is that of the device 14, 15 for sucking up debris and of the advance system 9–13. The pressure of the impact device 5 represents about two-thirds of the highest pressure, while the pressure of the rotary drive device 4 represents about one third of the highest pressure.
The essential advantage of this apparatus is its simplicity, because the supplies of the various movements are independent of one another and require no component other than distributors for carrying out all the functions.
The essential disadvantage lies in the significant pressure differences between the bodies of the flow splitter 16. Given the technology employed in this type of hydraulics component, these significant pressure differences give rise to leaks of hydraulic fluid between the splitter bodies, and this is manifested in a low hydraulic efficiency of the hydraulic supply device of the drilling apparatus.